The field of the invention relates to computed tomography and more particularly to methods of obtaining image data from X-rays passing through a body of a prone patient at oblique angles.
X-ray devices used for imaging and/or therapy are known. In the case of imaging, such devices are typically arranged to provide an x-ray source and detector on opposite sides of a body of a patient. The source and detector rotate in unison around the patient collecting x-ray data at discrete locations.
The x-ray source is often structured to allow X-rays to propagate through the body of the patient in the form of a fan beam. The detectors of a fan-beam device typically include an array of many individual detector elements, often arranged in the form of an arc, to detect x-rays along the spread of the fan beam.
Alternatively, the x-ray source may generate a cone beam of X-rays. The cone beam may be detected by a two-dimensional array of detectors, typically referred to as an area detector.
In operation, the source and detectors are rotated continuously around the patient, and the signals from the detectors are sampled at intervals of a few milliseconds, so that sets of x-ray absorption profiles are collected at many angular increments around the patient.
From the x-ray data, an associated computer may solve a matrix of equations, or use some other mathematical technique to obtain a measure of the x-ray absorption of each of a number of two-dimensional areas (or xe2x80x9cpixelsxe2x80x9d) within a finite thickness of the slice. The pixels may be combined to form a two-dimensional image of a cross-sectional view, or slice, through the patient""s body.
After each revolution, the patient may be moved a small distance in a direction normal to the plane of the slice, and the process of x-ray exposure, data collection, and computer data reduction may be repeated to obtain an image of an adjacent slice. The motion and process may be repeated any number of times. Alternatively, the patient may be moved continuously, so that the x-ray beam follows a helical path along the body. In devices employing a cone beam, several slices may be generated simultaneously.
By correlating the data among adjacent cross-sectional slices, a three-dimensional array of data may be obtained. From the three-dimensional array of data, three-dimensional images (or two-dimensional images at orientations different from the slices) can be created, which may be used to determine the location of tumors or other lesions.
In conventional X-ray CT machines, it is not always possible to direct the X-ray source or position the X-ray detector to optimize the collection of X-ray images. As a consequence, patients must often be arranged in uncomfortable positions to facilitate the collection of X-ray data. Because of the importance of CT, a need exists for a method of collecting X-ray data that is less dependent upon the position of the patient.
A method and apparatus are provided for performing computed tomography. The method includes the steps of moving one of an X-ray source and an X-ray detector parallel to a head-to-feet axis of a prone patient and collecting data from the X-ray detector as the one of the X-ray source and X-ray detector moves along the head-to-feet axis of the prone patient.